1959 ... atomic proof tank!

... during the 1950's everybody was gung-ho for duking it out on the 'nuclear battlefield'.
After all; if your troops couldn't survive on the charred plains of Armageddon what was the point in having an Army? Much of the bluster about the tactical nuclear weapons was part of the poker game to counter how outnumbered the NATO ground forces were versus the Warsaw Pact. War plans for fighting the a Communist invasion of Western Europe all involved a scenario of "we get pushed back to this point and then we use our nukes!"  Some of it made sense in the early 50's when the Soviets possessed no real ability to strike the United States directly. Then after the 1962 Cuban Missile Crisis US and NATO leaders began to look toward World War Three options that were a little more-open minded than 'destroy the entire world or surrender!'.

... anyway- it was apparent from all of those fun nuclear tests where they got to blow-up everything from planes, trains and split-level house (including the kitchen sink) that while heavily armored tanks got rolled over by the blast wave they otherwise were still usable.
You could ride out a small atomic bomb in the battlefield 5-20 kiloton range behind the
6 to 12 inch steel of a heavy tank. Outside would be a charred, radioactive mess. But you could drive around and shoot things until the radiation killed you in a day or two.

Hence the invention of the 'funny shaped blow-over proof' Russian tank. Ominously christened 'Object 279'. They only built one. Turned out to be too heavy to really go anywhere- tended to sink into the ground and collapse any bridge it tried to cross.

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